The present invention generally relates to liquid heating apparatus and, in a preferred embodiment thereof, more particularly relates to specially designed bottom pad/foam dam apparatus positionable under the tank and outer jacket portions of a water heater.
As conventionally constructed, a water heater typically has a tank portion adapted to hold a quantity of water to be heated, an outer jacket structure outwardly circumscribing the vertical tank side wall portion and forming an annular insulation space therewith, and a quantity of insulation disposed in this annular space. The bottom end of the tank/jacket structure is typically placed into a circular bottom pan structure and suitably secured thereto.
A common method of placing insulation in the tank/jacket annulus, after a bottom portion of the tank/jacket structure is secured within the bottom pan, is to simply inject liquid foam insulation into the annulus and let the injected foam subsequently harden therein. As is well known in this art, pressurized injected liquid insulation foam has an undesirable propensity for leaking out of the tank/jacket annulusxe2x80x94particularly at the interface between the bottom pan and the bottom tank/jacket portion received therein. In order to contain the injected liquid foam within the tank/jacket annulus, a variety of xe2x80x9cdamxe2x80x9d structures have previously been utilized to seal various leak paths leading outwardly from the annulus.
To block outward injected foam insulation leakage at the bottom pan, one proposed solution has been to install a bottom pad/foam dam member in the bottom pan and then rest the bottom end portion of the tank/jacket structure on the pad/dam member which is configured to block outward flow of injected foam insulation outwardly from the tank/jacket annulus adjacent the bottom pan. Examples of this technique, utilizing molded polystyrene bottom pad/foam dam structures, may be found in U.S. Pat. No. 5,924,392 to Hall and U.S. Pat. No. 5,154,140 to Windon.
While these previously utilized bottom pad/foam dam structures are generally satisfactory for their intended purpose, they are formed from a xe2x80x9ccrushablexe2x80x9d material (for example, molded polystyrene) which may permit an annular bottom end portion of the tank to crush and cut downwardly through the dam and come into contact with the underlying metal base pan, thereby creating an undesirable thermal leak path between the tank and the base pan. Additionally, the use of this type of bottom pad/foam dam structure has tended to complicate the provision of a desirable electrical grounding path between the tank and the underlying base pan.
A need thus exists for an improved bottom pad/foam structure of the type generally described above. It is to this need that the present invention is primarily directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a liquid heating device, representatively a water heater, is provided with a specially configured bottom pad/foam dam structure that is received in a bottom pan portion of the water heater and is used to support the tank and outer insulation jacket portions of the water heater in a manner operatively positioning the insulation jacket relative to the tank portion and preventing outflow at the bottom pan of liquid foam insulation injected into an insulation space between the jacket and tank portions of the water heater.
The bottom pad/foam dam structure illustratively includes a bottom pad/foam dam member formed from a generally crushable material such as molded polystyrene, the bottom pad/foam dam member being received in the bottom pan and having a top side with a first groove formed therein and receiving an annular lower end edge portion of the tank. To prevent the tank from vertically crushing the pad/dam member a substantially rigid support structure is imbedded in the pad/dam member beneath the first groove and vertically extends between the bottom pan and the bottom side of the first groove.
Preferably, the support structure is defined by a plurality of substantially rigid support members (representatively three in number) which are imbedded in the pad/dam member, are circumferentially spaced apart around the vertical tank axis, and vertically extend from the bottom pan to the bottom side of the first groove. In a preferred embodiment of the support members, one of them is formed from an electrically conductive material and forms an electrical grounding path between the tank and the bottom pan, and the other support members are formed from a thermally insulative material which desirably reduces the downward heat flow between the tank and the bottom pan. Alternatively, the electrical grounding path between the tank and the bottom pan is formed using a vertical metal grounding bolt extending through an upwardly indented central portion of the bottom wall of the pan and threaded into a metal bracket structure secured to the underside of the bottom head portion of the water heater tank.
According to a feature of the invention, the bottom pad/foam dam member is provided with an upwardly projecting foam deflection portion extending around a relatively small portion of its periphery. The deflection portion underlies a foam injection opening formed in a top end portion of the jacket and has circumferentially opposite sides which slope upwardly and circumferentially toward one another to form an apex at the top end of the foam deflection portion. When liquid insulation foam is injected inwardly through the injection opening, the foam impinges on the apex and is circumferentially deflected in opposite directions through the jacket/tank insulation space to facilitate the even circumferential distribution of the injected insulation therein.
In accordance with another aspect of the invention, an upwardly projecting seal tab is formed on a peripheral portion of the bottom pad/foam dam member and is used to form an insulation seal around an outwardly projecting tubular drain fitting on a lower end portion of the tank. The tab is pressed against an inner side surface portion of the jacket and has a horizontal opening therein which press-fittingly and sealingly receives the drain fitting.
In an alternate embodiment of the bottom pad/foam dam structure, an additional top side groove is formed in the pad/dam member to receive an annular bottom end edge portion of a differently sized tank. Accordingly, the same pad/dam member may be used in conjunction with two different water heaters having differently sized tank portions in this alternate embodiment of the bottom pad/foam dam structure the substantially rigid support members are each configured to underlie circumferential portions of each of the two tank edge grooves.